Revista de química analítica ambiental

The Effect of Moisture Content Variation on the Bioremediation of Hydrocarbon Contaminated Soils: Modeling and Experimental Investigation

Abstract

Fatemeh Bahmani, Seyed Ahmad Ataei and Mohammad Ali Mikaili Kherameh

This study reports the effect of water content variation on the rate of Total Petroleum Hydrocarbon (TPH) removal from a contaminated soil. For this purpose, four samples of the soil with weight of 2 kg were placed in identical beakers. The initial TPH content of the soil sample was 60 g kg-1, and the initial moisture content of the samples was adjusted to 60% of the field water holding capacity of the soil. The process of bioremediation was started by nutrient addition and inoculation of TPH degrading microorganisms to the soil. The water content of the samples was restored to the initial value intermittently by water addition. The frequency of water restoration, however, was different for the samples. For the first sample water was restored every two days, for the second sample every four days, for the third sample every 8 days, and finally for the fourth sample every 12 days. The process was continued for 90 days. Microbial counting showed that the number of total heterotrophic bacterial, and TPH degraders were increased significantly in all soil samples. Quantification of TPH residual in soil showed significant difference between the soil samples. For the soil sample with 2 day water restoration pattern, the TPH content decreased from 60 to 18.6 g kg-1. For other samples the degradation was significantly lower. For the soil sample with 12 day water restoration pattern the TPH content decreased from 60 to 42 g kg-1 during the process. A model was developed to predict moisture variation and TPH removal form the soil as a function of time. The model predicted the experimental reasonably well.